It is known that epoxides may be carbonylated by reaction with carbon monoxide. The primary product of the carbonylation reaction is a .beta.-propiolactone formed by insertion of a carbonyl group into a carbon oxygen bond of the oxirane group of the epoxide. Secondary products, such as .beta.-propiolactone polymers, 3-hydroxycarboxylic acids and esters, and acrylic acids and esters, may also be formed directly or indirectly under specific conditions due to the reactive nature of the primary .beta.-propiolactone product.
According to GB-A-1020575 the carbonylation reaction requires the presence of a metal carbonyl catalyst such as a cobalt carbonyl catalyst. In GB-1020575, using ethylene oxide as substrate, .beta.-propiolactone is obtained as primary product, whereas the presence of metal halides or quaternary ammonium halides promoted the formation of .beta.-propiolactone polymer. It further discloses that the tendency of 1,2-epoxides to homopolymerize may be diminished by adding a small proportion of a base, such as pyridine, to the reaction mixture.
U.S. Pat. No. 3,260,783 discloses reacting ethylene oxide with carbon monoxide in anhydrous alcoholic solution. This process uses a cobalt carbonyl catalyst, which preferably is modified by a tertiary phosphine or tertiary amine co-catalyst including N-heterocycles such as pyridine and methylpyridine. A similar process is disclosed by Y. Kawabata, et al., in Nippon Kagaku Kaishi, (5), 635-40 (1979).
U.S. Pat. No. 2,782,226 discloses a process where ethylene oxide is allowed to react with carbon monoxide and water in the presence of cobalt on kieselguhr catalyst to form monoethylene glycol hydracrylate (ethylene glycol monoester of 3-hydroxypropionic acid). The ethylene glycol monoester of 3-hydroxypropionic acid as end product is obtained through the addition of a further ethylene oxide molecule to the intermediate 3-hydroxypropionic acid reaction product.
U.S. Pat. No. 4,209,467 discloses catalyst which is a reaction product of a cobalt carbonyl compound and a hydroxy substituted pyridine compound, which are used in the hydroformylation of olefins to aldehydes.
While it is known that epoxides can be carbonylated to produce .beta.-propiolactones and derivatives, the exemplified catalyst systems leave room for improvement in terms of achievable selectivity and reaction rate in order to arrive at an industrially competitive process.
It is therefore an object of the present invention to provide an epoxide carbonylation process with improved selectivity and/or reaction rate to produce .beta.-propiolactones and/or derivatives thereof.